Question

How do I convert a DateTime from the local timezone returned by DateTime.Now to another timezone than Utc. On desktop we have the TimeZoneInfo.ConvertTimeBySystemTimeZoneId(), but it’s not available on windows phone!

This java snippet shows roughtly what I want to do

SimpleDateFormat format = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss z", Locale.US); 
TimeZone tz = TimeZone.getDefault();
format.setTimeZone(TimeZone.getTimeZone("GMT"));
str = format.format(new Date());

Answer 1

This is not possible to do using the system libraries as there is no way to create TimeZoneInfo objects other than local and utc. They have also sealed the class.

You can however use this simple library to enable conversion to non-local time zones.
https://nuget.org/packages/WinRTTimeZones

Use it like this:

using TimeZones;    

public void ConvertTime()
{
    // Get the time zone we want

    var tz = TimeZoneService.FindSystemTimeZoneById("Central Standard Time");
    var dt = new DateTime(1990, 7, 1, 12, 0, 0, DateTimeKind.Utc);

    // This time will be central time
    var local = tz.ConvertTime(dt);
}

When the DateTime is converted it is an easy exercise to format it as you want. I recommend to format the date in the local format (not the local timezone) to make easy for the user to understand the date.